This invention pertains to the art of providing a control box and electrical wiring arrangement for the electrical power and control system for a transport refrigeration unit.
Transport refrigeration units, such as are used to refrigerate freight containers and trailers, may take various forms with respect to their power sources and control systems. A typical transport refrigeration unit, adapted for use on a container which may alternatively be carried aboard ship at sea, or by truck or train on land, will be arranged to be powered either from an electrical power source when available, or by an internal combustion engine when suitable electrical power is not available. Thus, when the containers are aboard ship or at dock side, the refrigeration units will usually be powered by an electrical source from the ships power or from dockside power. When being transported by truck on land, the units will usually be powered by the internal combustion engines.
These units are reasonably sophisticated in order to properly carry out their functions and accordingly contain a fairly large number of control elements associated with both the refrigeration system and the engine circuit, these elements including both controlling and indicating elements. Since the value of the refrigerated cargo carried will usually some multiple of the value of the refrigeration unit itself, it is relatively important that failures and malfunctions of the refrigeration unit be repairable ordinarily within a reasonable time. Since the repair or replacement of parts may also have to be carried out under adverse conditions at times, such as when the unit is refrigerating a container which may be at the top of a stack of container units aboard ship, the arrangement should be such that the replacement of parts can be easily and quickly effected.
To promote repair and replacement of malfunctioning control elements, there is usually an effort to locate together those control elements not required to be located remotely because of their function. With most of the control elements centralized at what is called a control box, it is apparent that a fairly common reason for a malfunction of the unit as a whole will be as a result of failure of one of these centrally located elements.
Accordingly, it is among the aims of the invention to provide a control box arrangement of wiring and controls at the control box which facilitates repair and replacement of any parts, and which also is arranged to promote safety during the repair and operation of the units. Also the arrangement is intended to permit the quick determination of any assembly of parts which requires repair or replacement.